The present invention relates to a level position measuring method, level marking method and level marking apparatus comprising a tube, capable of directly measuring a height.
Up to now, the basic of level marking in constructions is such that the level marking begins with marking a horizontal line mark as a primary mark (a parent mark) on a surface of a builiding frame and a pillar of a building. Level positions of a ceiling, floor, sashes and fittings are figured by marks measured based on the horizontal line mark. Such marks are so-called a child mark (secondary line mark).
As a prior art, there is a level measuring apparatus in combination of a staff having a scale on the surface thereof and a optical-type level which reads the scale of the staff. The disadvantage of this optical-type apparatus is that the scale of the staff is often misread. According to this prior art, a staff is placed in a certain position and the scale thereof is read from both the front and back sides by the optical-type level. Then a certain height calculated beforehand is added thereto and marking is done manually. This process has to be repeatedly done. Another disadvantage of this prior art is that it requires an assistant besides an operator. Further, it also requires a good skilled and well experienced operator to complete the level marking successfully.
Concering these disadvantages, there is a laser-beam-type level which releases a laser beam to a staff. The disadvantage of this laser-beam-type level is that a spot of the laser-beam on the scale of the staff is rather large, so that it lacks accuracy of measurement.
A mutual disadvantage of both the optical-type and the laser-type levels is that actual marking process is done by human hands. Thus it also lacks accuracy of level measurement. Another mutual disadvantage is that the measurement can only be performed at an open space in which there is no obstacle between the level and the staff, which disturbs a pass way of the light and the laser beam. In case there is any obstacle, it should be removed or the level or the staff should be replaced.
A leveling tube, another prior art, is used at a place such as a small room in which a level cannot be used and leveling accuracy is not highly required. A leveling tube is widely used because it is inexpensive compared to an apparatus such as a laser-type level, and it is easy to use for any workers. A leveling tube is shown in FIG. 9. The leveling tube comprises a pair of transparent pipes 1, 1' connected to each other by a rubber hose 2, and it is arranged such that the water level 3, 3' of the water 4 filled in the pipes 1, 1' is observable from outside.
The principle of the leveling tube is that the water level 3 in the tube 1 is equal to the other water level 3' in the tube 1', so that when the water level 3 is adjusted to the reference level, the other water level 3' indicates the same level.
The leveling tube is inexpensive compared to a optical-type level and a laser-type level, and it can be used in places that a optical-type or a laser-type level cannot be used because obstacles such as walles disturb a runway of the light or laser beam, so long as the rubber tube 2 reaches. The disadvantage of the leveling tube is that the water 4 in the tube spills since both edges of the hose are not sealed. Another disadvantage thereof is that it takes some time for the water level is stabilize.
The applicant of the present invention filed an patent application (Japanese patent application No. 4-38752) for an invention which resolved the spilling problem and stabilizing problem of the leveling tube. The invention is such, as shown in FIG. 10, that one end of the tube 5 is airtightly closed, so that the water does not spill even from the other end of the tube which is still open to the atmosphere, and that the fluidity of the water in the tube is more stable, enabling the level measurement more accurately.
The structure of this prior invention is such that water is filled in a tube, one end thereof is airtightly closed by securing a pressure sensor thereto and the other end thereof is widely open. A level or any height can be measured as such that the pressure sensor indicates zero when the water level of the closed end comes to the level equal to the level of the open end of the tube, and the pressure sensor indicates positive pressure when the water level of the closed end is lower than that of the open end. In the same manner, the pressure sensor indicates negative pressure when the water level of the closed end is higher than that of the open end of the tube.
According to the optical-type and laser-type levels, they require to draw secondary line marks based on a horizontal line mark. That is, each level of the prior art can only indicate a level of the apparatus. As shown in FIGS. 11 (a) and (b), when a certain level is to be measured and the level differ from that of the apparatus, the level of the apparatus is measured at first, then a difference (h) between the certain level and the level of the apparatus, which is figured out beforehand, is added using a scale to the level of the apparatus and a marking is done thereto. That is, in most cases, levels cannot be directly measured or marked, instead, drawing a secondary line mark based on the primary line mark is required.
According to the prior art already filed by the applicant of the present invention, a number of technical problems which should be resolved have been found as it was examined at a tough condition of construction field. At a construction field, the apparatus of the prior art is often affected by outer force such as wind, vibration, temperature and accidents, so that the inner pressure of the tube often varies depending on such conditions, which unstabilizes the water level of the open end of the tube and an output of the electric pressure of the pressure sensor, causing the measurement inaccurate.
The object of the present invention, an innovated invention of the applicant, is to provide a level position measuring method, level marking method and level marking apparatus comprising a tube capable of directly measuring a certain height, without being affected by outer causes at construction fields.